AIR INLET SILENCER

TM 55-4920-424-13&P

1-29. AIR INLET SILENCER. (See figure 1-3.)

1-30. The air inlet silencer is a sound suppressor, bolted to thin blocks on the forward left side of the trailer. The silencer

consists of a labyrinth-type annular muffler, lined with acoustical material, a 90-degree adapter elbow, a flexible coupling,

and clamps. During engine operation, the air inlet silencer is clamped to the air inlet shroud of the APU. The labyrinth

formed by the insulated silencer assembly reduces the noise of intake air to the APU during engine operation.

1-31. EXHAUST DUCT ASSEMBLY. (See figure 1-3.)

1-32. The exhaust duct assembly is a welded assembly bolted to the frame at the forward end of the trailer. The exhaust

duct assembly consists of two duct halves, six support angles, and four mounting plates. The exhaust duct assembly

directs the APU exhaust and noise upward.

1-33. SPEED INCREASER. (See figure 1-3.)

1-34. The speed increaser, mounted on a support frame that is bolted to the trailer, incorporates an axial (straight-

through), 6000-rpm pad on which the dc starter-generator is mounted, and a right-angle, 8000-rpm pad on which the ac

generator is mounted. The APU is mounted on the speed increaser, and through the APU output speed of 6000 rpm, the

speed increaser drives the generators at their respective speeds. The speed increaser is self-contained with an integral

oil sump and a splash oil lubricating system.

1-35. FIRE EXTINGUISHER. (See figure 1-3.)

1-36. The portable, manually-operated, fire extinguisher is mounted in a support bracket at the aft, right end of the trailer,

and secured in place by a clamp attached to the fire extinguisher support bracket. The fire extinguisher is a 2.5-pound dry

chemical type extinguisher.

1-37. TRAILER ASSEMBLY. (See figure 1-3.)

1-38. The trailer provides the base and mounting provisions for the check stand components and the APU. The chassis

frame consists of aluminum sheets welded into a platform on which the APU and speed increaser support frame is

mounted. The chassis frame is supported on the rear axle by a pivot plate bolted to the chassis frame, and with drag links

mounted in automotive-type rubber bushings. The chassis frame is supported on the front axle by a plate bolted to the

chassis frame and secured to the axle with U-bolts. A towbar, pivoting on the front axle and controlling tie rods to the front

wheels, provides steering for the trailer. The rear wheels are equipped with a mechanical parking brake system,

connected by linkage to a brake handle on the left side of the trailer. The parking brake mechanical linkage is welded to

the fuel tank. The four, split-rim wheels are mounted with pneumatic tires and tubes. Tiedown rings and reflectors are

bolted on the side of the chassis frame.

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